The Primary Objective of This Single-center observational Study is to Investigate the SARS-CoV-2 Spike Glycoprotein RBD Antibody Concentration in Saliva and Serum in Healthy Non Vaccinated and Non-SARS-CoV-2 Infected, COVID-19 Convalescents, Persons Vaccinated With Pfizer-BioNTech BNT162b2, Moderna mRNA-1273 or AstraZeneca ChAdOx1 nCov-19 AZD1222 Vaccines, and Convalescent COVID-19 Patients That Have Subsequently Been Vaccinated.

A Potential Difference in the Immunoglobulin Concentrations of the Pfizer-BioNTech BNT162b2 Vaccine, Moderna mRNA-1273 vaccine, and the AstraZeneca ChAdOx1-S Vaccine Will be Uncovered.

This Knowledge About the Mucosal Immunity Will be Important for Further Designing of Vaccine Strategies.